Synchronizing bomb sight



nec. 19, 195o T. H. BARTH 2,534,397

sYNcHRoNIzING BOMB SIGHT Filed April 5, 1935 12 sheets-sen 1 Dec. 19, 1950 T. H. BARTH sYNcHRoNIzING Bows slam` 1'2 Sheets-Sheet 2 Filed April 5,11935 Dec. 19, 1950 T. H. BARTH sYNcHRoNIzING Bows SIGHT 12 Sheets-Sheet 3 Filed April 5, 1935 Dec. 19, 1950 T. H. BARTH 2,5345397 sYNcHRoNIzING BOMB SIGHT Filed April 5, 1935 12 sheets-sheet 4 Dec. 19,1950 v T. H. BARTH 2,534,397

sYNcHRoNIzING BOMB SIGHT v Filed April 5, 1955 12 shuts-sheet 5 Dec. 19, 1950 1.'. H. BARTH 2,534,397

' sYNcHRoNIzING BOMB SIGHT f Filed April 5, 1955 12 Sheets-Sheet 6 lic'.' l 9 Dec. l), 1950 T. H. BARTH 2,534,397

SYNCHRONIZING BOMB SIGHT Filed April 5, 1955 12 Sheets-Sheet '7 76 U/'awr meg Dec. 19, 1950 .Y T. H. BARTH 2,534,397

SYNCHRONIZING BDMB SIGHT Filed April 5, 1955 12 Sheets-Sheet 8 Dec. 19, 1950 T. H. BARTH 2,534,397

SYNCHRONIZING BOMB SIGHT Filed April 5, 1935 12 sheets-sheet 9 21 233 VITO /92 /S/ 20/ /ez l m l 247 206 238 2/6 o o 26, 21s zZ/ p I s 211 o 242 A 2' De.l19, 195o T. H. BARTH SYNCHRONIZING BOMB SIGHT Filed April 5, 1935 12 Sheets-Sheet l0 Dec. 19, 1950 Filed April 5, 1935 SYNCHRONIZING BOMB SIGHT T. H. BARTH 2,534,397

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Dec. 19, 1950 T. H. BARTH 2,534,3.97

` Y sYNcHRoNIzING BOMB SIGHT Filed Apr1"\5, 1935 l2 Sheets-Sheet 12 Patented Dec. 19, 195() UNITED STATES PATENT OFFICE ASYNCHRONIZING: BOMB SIGHT (Cl. 33--46L5 I7 Claims.

inventionA relates to a sight for use in dropping bombs from aircraft, andv more particularly to a sight of that type having a sighting element that is movable to keep a target in the field of viewA as the craft approaches such target and variable speed mechanism to actuate the sighting element, commonly known as a synchronizing sight.

Among the several objects of this invention are:

To provide a synchronizing bomb sighthaving all its moving parts completely enclosed in a weather-tight casing.;

To' provide. means for automatically releasing the. bombs when the bomb carrying craft isV in the proper position and which lvvill prevent the inadvertent dropping of bombs by such automatic release;

To provide automatic means-in a. bomb sight toi correct for the crossy trail of a bomb;

To improve. the clutchv used to connect the: sight proper to an azimuth .stabilizing gym- With the above andother objects in View, this invention consists in the construction, combination. and arrangement of .parts as 'Will'be described more fully hereinafter.

The present invention is in general similar 'to theY bomb sight shown in my copending application Serial No. 635,298 led September 28,1932,

now Patent No. 2,438,532, granted March 30, 1948, i

bomb sight involves the proportionality of theV homologous sides of similar triangles. If anl object on the .groundV be kept in the field of View of a telescope onl an aircraft by turning. the telescope about a transverse axis intermediate its ends, a member connected to the telescope on a line passing transversely through the optical axis of the telescope and mounted to slide horizontally in .a plane parallel to the plane of swing of. the telescope passes through. a distance that hasthe same ratio to the ground distance covered by the craft as has the distance ofthe point of.` connection oi'that Vmember to .the telescope from the axis of rotation to the distance of. the object on the ground from the same axis of rotation. Consequently, if the horizontally moving member `be causedto travel .at theproper speed, which isa function of the altitude and the speed of the-craft, an object visible in the telescope will remainl in the Yiield thereof throughout the rotation .of the telescope.

As used throughout `this specication. and; the

claim-s thereto, appended; the term front refersl tothat sideof the instrument' next the operator, and back refers to the opposite side thereof right-hand.` andi left-hand refer tothe relative positions' of the' `of the instrument as seen from theooperators position'.

In the drawings:

Eig.. l' isan-A elevation or theback. of the complete sight and azimuth stabilizer;

Fig; 2: shows the assembly or the stable vertical. gy-ro, the' telescope and parts 0fI the automaticl Figs. 9: and .9a are detailvieivs of alternative formsof the ground speed indicator;

Fig, l0 is a detail View of the driving mechanism immediately associated with the sighting, telescope;

Figs. l1 and l2 are side elevational details of, the range bar and the ground speed bar, respectively;

Fig. 13 is a. side elevation of the telescope asserrrbled in the supporting cradle therefor;

Fig. ldshows` the sarne parts as Fig. 1'3 on a line at rightfangles to Fig. 13;

Fig.. 1.5 is a detail View of the ground speed` segment.;

Fig.l 16 isa detailview of the range segment;

Fig. 17l is a top plan view of the azimuth stabilizer .and pilotdirector assembly;

Figs.` 18 and 19A are details of the clutch for connecting the azimuth stabilizer tov the sight proper;

Fig. 20' is a sectional detail showing the sleeve in which the spindle that supports the sight proper is' mounted;

Fig'. '21 is asidek elevation of the azimuth4 stabilizer mechanism showing the electromagnetic clutches thereof;

Fig. 22 is an elevational View of one side of the azimuth stabilizing .gyro and the commutator associated therewith;

.Figs 23, 24, 25 vand 26 illustrate various details of `the automatic cross trail mechanism.;

Fig;l 2.7 isa wiring `diagram of the bomb sight andipilot director assembly;

Fig. 28 is an elevational View of the inner face of the plate that carries the operating knob and the synchronizing knob;

Fig. 29 is a detail View of part of the trail correction device.

The sight proper is enclosed by a lower casing -member 28 (Fig. 5) supported on spindle 29 that is rotatably mounted in the azimuth stabilizer casing 3D (Fig. l) and by upper casing member 3| that is detachably secured to casing member 28. Transparent windows 3|' and 28 are provided in upper and lower casing members 3| and 28, respectively, adjacent the upper and lower ends of the sighting telescope to protect the mechanism from the weather while leaving the line of sight unobstructed in all possible angular positions of the telescope. Pivotally mounted in antifriction bearings at the ends of lower casing member 28 is the normally athwartship cardan 33 (Fig. 4), in one end of which is mounted the sight stabilizing gyro 34 upon trunnions 35 that lie at right angles to the Cardan bearings, the spin axis of gyro 34 being vertical to provide a stable vertical for the sighting telescope 36 that also is mounted in cardan 33 as will be hereinafter described.

Upon the upper surface of the casing of gyro 34 are fore-and-aft level 31', athwartship level 31, movable weights 35 and 39 for statically balancing the gyro and a forwardly and upwardly inclined pin 4|] adapted to be engaged by a longitudinally slidable sleeve 4| to lock the gyro against movement when not in use. Knobs 43 and 42 are slidable toward and away from casing member 28 and are connected to friction rollers which, when the knobs are pushed in and rotated, will tilt the gyro 34 athwartship and fore-and-aft, respectively, to level the gyro.

Telescope 35 (Fig. 4) is rotatable in bearings 44 (Fig. 13) carried by cradle 45 that is mounted on trunnions 46 carried by cardan 33, whereby the cradle may rock athwartship and the telescope be rotated in a fore-and-aft plane. A gear sector 41 is secured to the telescope and meshes with a pinion 48 that is xed on the same shaft as is cable drum said shaft being rotatably mounted in a bearing on cradle 45. A Very light flexible cable 56 (Fig. l0) is attached at one end to cable drum 49 and is in part wound on the drum, passes around sheaves and 52 carried by cardan 33 through the axis of the right-hand Cardan trunnion, around a sheave 53 mounted on the outer face of the right-hand end of casing member 2B and thence to a cable drum 54 upon which also a part of the cable is wound and to which the other end thereof is attached. It is to be noted that cable 55 passes axially through trunnion 46 of cradle 45 and also through the Cardan trunnion to prevent the pull of the cable from exerting any tilting force upon either the cradle or the cardan. The length of free cable, between sheaves, where the cable passes through the cradle trunnion and also through the Cardan trunnion is suilicient to prevent detrimental twisting thereof by rocking of either the cradle or the trunnion. The cable 55) is preferably made of a large number of very fine strands of phosphor bronze wire which gives great ilexibility with practically no stretch. To provide for adjusting the tenston of cable 50 sheave 54 is secured to shaft 55 by means of a member 56 (Fig. 6) that clamps upon shaft 55 and is connected to sheave 54 by a screw 51.

The angular position of the telescope with respect to the vertical is indicated by calibration lines on an arcuate member 36 (Fig. 14) adjacent the ocular end of the telescope.

A flat clock spring is mounted in a housing 58 at the side of telescope 36 and has one of its ends attached to the telescope and the other end xed to housing 58, which is concentric with the bearing 44 of telescope 36 and is secured to cradle 45. The winding of the spring is such that it tends always to move the ocular lens of the telescope (visible in Fig. 4) toward the front of the sight thus keeping cable 5] always under tension. When the eyepiece of the telescope is moved forward the clock spring is wound up and hence it rotates telescope 36 toward the operator when the pull upon cable 55 is relaxed. The mechanism for operating the telescope is shown in Figs. 6, '1 and 8.

The shaft 59 (Fig. '1) of servomotor 6E] is prolonged to carry a pinion 6| and a governor mechanism 62 (the latter being of a type shown in my copending application Serial No. 551,008 led July 15, 1931, now Patent 1,936,577 granted Nov. 28, 1933) that separates a pair of contacts 63 (Fig. 21) to interrupt the supply of current to motor 6U when the speed of the motor exceeds a predetermined value which depends upon the altitude from which the bombs are to be dropped, thus slowing down motor 65 to the proper speed. A knob 64 (Fig. 8) having on its periphery calibrations in terms of altitude may be turned to vary the spring tension acting upon governor 52 to obtain the correct speed for the given altitude. A second altitude scale on knob 54 indicates the settings to be used at different altitudes when the ground speed is to be determined, as described hereinafter. Since the characteristics of the fall of diiel'enttypes of bombs are not the same, a plurality of interchangeable knobs 64 each suitably calibrated for a type of bomb is provided. Pinion 6| meshes with teeth on the periphery of a disk 65 that is held in assured contact with the roller 61 (Fig. 6) by means of a spring 66 held under compression on the Shaft of disk 65 to urge the disk outwardly against the roller 61 which is driven thereby. The roller 61 is mounted in a bracket 68 that is in screw-threaded engagement with screw spindle 65 and is moved longitudinally of the spindle when the spindle is rotated, which shifts roller 61 radially on disk 65. It is to be understood that the portion of roller 61 that contacts disk 65 is on the opposite side of bracket 68 from the part shown in Fig. 6. The shaft of roller 61 is toothed to form an elongated pinion 1U that is meshed with a gear 1| carried on a shaft upon which is fixed a pinion 12. The pinion 12 is meshed with a gear 13 to which is rigidly connected one gear 14 of a differential gear assembly. Pinions 15 of the differential engage the gear 16 which is rotatable on shaft 18 but is securely fixed to gear 11. The pinions 15 are in driving connection with a shaft 18 upon which is a pinion 19 and a beveled pinion 85. It is apparent that if the gear 11 be locked against rotation when pinion 15 is rotating, pinions 15 will be driven through gears 1 I, 12, 13 and 14 and caused to travel around gear 16 thereby rotating shaft 18, but if the gear 11 be free, the only result of driving the pinions 15 will be to rotate geai` 11 upon shaft 18.

Ground speed rack bar 8| (Fig. l2) is mounted to slide horizontally and has its teeth engaged with pinion 19. A pin 82 on bar 8| is slidable in the radially extending slot bar 83 (Fig. 6) xed to ground speed segment 84 (Figs. 6, l5) which is mounted to be rotatable about a member fixed to the end of the sight casing. The radial center line of slot bar 83 and the optic axis of the telehence no errors due toa difference in angular positions of the two can beintroduced. Upon a portion. of the segment 84 are teeth 85r (Figi 15) meshed with a pinion 85 fixed on shaft 55` to rotate the cable drum 54. One edge of segment 84- is an arc of a circle and has formed therein a notch 81 intowhich arm connected to the automatic release switch vdrops at theY proper time as will be hereinafter set forth. A radially extend-- ing member Si? is fixed to the segment 8'4 toy co operate with the scale 8.9 (Fig. 4) calibrated in degrees of arc with its zero point corresponding to the vertical position of telescope 3'5;V at the time of dropping the bomb, the member 38 indicates on scale Se the dropping angle.

A roller St is mounted on the' bracket 68 (Fig. 6) and' may ride against a track* 8 to prevent the roller 51 from being swung too far out of its illustrated position by the 'pressure of disk` 65 thereagainst.

A beveled pinion S2 is connected to the lower end of screw (it and on the upper end of that screw is secured a pinion S3 nthat is meshed with a gear @4 on a shaft e5 to which pinion Se also is i'lxed, the last mentioned pinion being meshed with rack teeth on horizontally slidable range bar 9'! (Fig. 11). A pin 98 that extends laterally from range bar Siy is slidably disposed in slot 99 in the range segment iii@ (Figs. 6, 16) which is mounted o coaxially with the ground speed segment 84 and carries index ite which is disposed adjacent a scale lill (Fig. 4) to indicate the tangent of the range angle. A stud |62 carried by segment lila serves as the pivot for arm |33 (Figs. 6, 27) of the i' automatic release switch whereof one blade |54 is carried by an insulating member `HB6 non-rotatably secured to arm |03, while the: bifurcated blade it?, between the arms of which blade |04 l is received to make contact, is fixed to the segment itil. A spring. Hi8 having oneendzattaohed to range segment HID and` the other to member H25 tends to draw blade |84' into contact with.

blade lill but.` the contact is prevented so long as I, arm m3 rides. upon the periphery of the.` arcuate portion of segment 84. However, as the seg-ment 84 is rotated?, the notch 5'! is moved into position so that arm` is@ Imay drop` intothe notch and the blades i84- and it?Y be brought into contactthrough the action of spring |35, thus closing the automatic release circuit and dropping the bomb. Under the stress of a bombing run the operator might forget to` sto-p the mechanism. with theresult that the automatic release ywould be again actuatedaft-er theV telescope had been returned' to its original position and one or more bombs inadvertently dropped.V To-guard against this contingency a curved iinger |09 (Fig. 6) is disposed' with its free end in the path of the tip of the arm 33 to prevent the closing of the automatic release switch unless lever I HlY is lifted to rotate the disk i upon which the finger S9 is secu-red and so swing the free end of the iinger inwardly to an inoperative position, a spring ||2 being provided to move lever H0 downwardly as soonl as the lever is released by the operator.

Rotation of bevel pinion 92 will cause the bracket 5.58 to move up 0r down, since the screw 69 isthreaded therein, thus changing the distance of the point of contact yof roller 61' With disk 65 from the center of the disk and varying the rate at which pinion le and the gears connected theretoare driven. Any rotation of the screw 69 will be transmitted through pinion 93, gear 94, shaft 95 and pinion `et to range bar 97 which turnlwillf shift 'the position of the rangeV segment |100.

The purpose of moving theY roller 61 on 65 isto cause telescope 36 to be rotated at sucha ratev as to synchronize its movement with the apparent movementof a target and so keep the target inthe field of the telescope. Itis apparent that the rate of rotation of telescope 36 for synchronism is a function of both the altitude of thev craft and its speed with respect to the ground; the. greater the altitude the closer roller 67 will be tov the centerv of disk 65for any given ground speed. However, since the range angle, or dropping angle, is a function of. the time of fall of the` bomb; -which is one-fourth the square root of the alti-- tude, the' rotational speed of disk 55 must bel changed in inve-rse proportion tothe square root' of the altitude to impart 'the correct relative rate of movement to the ground speed bar andlk telescope, which rate mustbe inversely proportional tothe altitude.

Inasr-nuch as the position ofrange bar 37| is aY function of the ground speed and altitude itmay be usedf to operate a ground speed indicator of which one form is shown in Figs. 6 and 9,l but when so used, the speed of disk 65 must be oontrolledby the-second calibration on knob `|54', as mentioned above. This comprises a drum H3Y having inscri-boden its periphery calibrationsrepresenting grou-nd speed. In a groove H4 formedon the side of the drum, a cable .|\|5'is wound and has` one end attached to the drum, the other end? being securedJ to-pin Ht on range bar 91'. A flat spiral spring |A i 'i is disposed within the drum with one end attached to the drumand the other'end fixed to the stationary shaft H8Y upon which the drum rotates. The spring I |'i tends to rotate the drum |f|3 ina counter-clockwise direction as seen in Fig. 6- and thus movement of range bar 91 vto the left in that figure winds upV the-spring. The point at which thecalibra-tions on drum |3- are to be read is indicated byanindex H9 visible through a window |29. An alternative form of the ground speed indicator is shown in Fig. 9c in ywhich the range baris provided with rack teeth |2'| on its upper surf-ace to engagea pinion |22 that is fixed to `drum H3, the remainder of the structureA being the same Vas in Fig. 9; It should be noted that when the speed of disk' 65 is set for bombing it is not correct for the vdetermination of ground speed, and vice versa.

The actuating Vmechanism is manipulated by means of operating knob |23 (Fig. 1) and synchronizing, knob |24 carried by a plate |25 that seats upon theY plane faced flange |23 (Fig. 8). synchronizing knob |24 is fixed to one end of a hollow shaft upon the other end of which is a gear |121 (Fig. 28)' vrneshed with gear |28 (Figs. '7, 8) secured on a shaft 129 Vthat has secured on it 'a beveled pinion |38 that engages theV pinion 92 in Fig; 6. Operating knob |23 (Fig. 1) is fixed to a'shaft, also hollo-w, that is disposed within the shaft that carries knob |24. Splined in the shaft of knob |23 is a rod |3| having a head |32 on its outer' end and a pin |33 extending transversely therethrough adjacent its inner end, which pin is engageable with the notches in a crown gear |34 on a shaft having a spur gear |35 that meshes with gear l1 in Fig. 6. A knurled knob- |36 (Fig. 8) is carried on a shaft |31 that has xed to its other end a beveled gear |38 (Fig. 7) that may be moved into engagement with beveled gear! in Fig. 6 but is normally held out of mesh therewith by a spring that moves the shaft |31 outwardly. It will thus be seen that turning' the synchronizing knob |24 will rotate the screw 69 which causes the roller 61 to be moved radially on disk 65 and also shifts range bar 91 to the right or the left depending upon the direction of rotation of the knob. The knob |36 is connected to ground speed bar 8| by means of pinions |38, 86 and 19 and since the ground speed bar 8| is connected to range segment 84, by turning the knob |36 a rapid movement may be imparted to telescope 36. Slower setting of the telescope is accomplished by pushing in the head |32 whereby the operating knob- |23 is connected to the gear 11 which, in turn, is connected to ground speed bar 8| through shaft 18 and pinion 19. The telescope cannot be shifted by means of knob |36 if knob |23 is clutched in, owing to the disadvantageous gear ratios through which the operation would have to be effected.

As is well known, the effect of air resistance upon a falling bomb is to cause the bomb to lag behind the craft from which it is dropped so that the craft will be vertically above a point beyond the target at the time the bomb strikes. The angle between the Vertical line to the airplane and a line from the plane to the target at the time of impact of the bomb is known as the trail angle and to insure accurate dropping of the bomb, this angle must be corrected for in setting the dropping angle. The mechanism for making this correction comprises a semi-circular plate |39 (Figs. 1, 3) upon which are inscribed a series of curves |46 that give the characteristics of the fall of a particular type of bomb at dierent air speeds and has a scale I4| of mils on its edge. A lever |42 having on it a scale |43 to show altitudes is pivoted at the center ci plate |39 and is connected by shaft |44 to a gear |45 (Fig. 7) that meshes with gear |46 (Fig. 6). The gear |46 has internal threads (Fig. 29) that are engaged with external threads on sleeve |41 integral with upper screw spindle bearing 69', the gear |46 being disposed to rotate about an extension of screw spindle 69 independently of the screw spindle as to rotational movement but is connected thereto by means of thrust washer |46 to move member 69 longitudinally. Movement of lever |42 over plate |39 rotates gear |45 which, in turn, drives gear |46, causing the latter gear to be moved longitudinally due to its being in threaded connection with the iixed bearing 69', which 'produces a longitudinal shifting of screw member 69 and with it the roller 61 carried thereby and thus the rate at which telescope 36 is driven is varied to the proper degree to correct for the trail angle. By setting the altitude mark on lever |42 which represents the height 'l at which the craft is flying to coincide with curve |46 representing the speed of the plane, the proper trail correction, is applied. A spring |48 acts upon the screw spindle 69 to prevent longitudinal instability thereof due to its freedom of movement in that direction and also to move the spindle down when gear |46 is moved downwardly on sleeve |41.

If the bombing craft is not moving directly It is apparent that after the pensate for such changes. The mechanism by which this correction is introduced is shown in Figs. 2, 23, 24, 25 and 26.

As shown in Fig. 23, a stem |49 is disposed in the axial bore in spindle 29 that supports the sight casing. At the upper end of this stem is a head |50 with its greatest dimension disposed transversely of casing member 28 and having flanges |5| extending laterally therefrom. A member |52 having in it a recess corresponding to the shape of head |58 is slidably mounted on the head and has a stud |53 projecting from its upper surface. A strap |54 is engaged with member |52 and is non-rotatably connected to a bar |55 having on it a radially extended ange |56 and an index |51 secured to its outer end. A sleeve |58 is held between flange |56 and index |51 to be rotatable on bar |55 but not slidable thereon. Upon the outer face |59 of the sleeve |58 are calibrations |65 representing cross trail angles. Internal threads |6| in sleeve |58 are engaged with corresponding threads on a member |62 fixed to casing member 28. It is apparent that rotation of sleeve |58 to set one of the calibrations |68 in registry with index |51 results in a longitudinal movement of the sleeve which is transmitted to the member |52 that carries stud |53.

A guide member |63 is fixed to the inner face of casing member 28 at substantially its lowest portion and extends longitudinally thereof Base |64 of yoke |65 has beveled edges that are slidable in undercut grooves |66 in the member |63 and a transverse slot |61 in base |64 is so disposed that stud |53 is slidable therein. Fixed to cross member 33 of cardan 33 is a bearing member |68 in which is journaled a shaft |69, there being an arm |18 xed to one end of shaft |69 and a second arm |1I xed to the other end thereof. The arm |18 carries a stem |12 upon the free end of which is a ball |13 that is operatively engaged with yoke |65. By means of a pin |14 on arm |1| and a retaining spring |15 cooperating therewith, arm |1| is connected to u one end of a link |16 whereof the other end is connected to lever |11 that is pivotally mounted intermediate its ends on cradle 45, the other end of lever |11 being connected to a link |18 which connects cradle 45 and gyro 34 for stabilizing the cradle. When sleeve |58 is set with the zero point of calibrations |68 in coincidence with index |51, stud |53 is concentric with stem |49 and spindle 29 and rotation of casing 28 about the axis of spindle 29 produces no movement of the cross trail correction device. However, when sleeve |55 is turned away from the zero position, stud |53 is oset from the center of rotation of spindle 29 and since stern |49 is held against rotation by a set screw |19 that is threaded in a xed bracket |68, any turning of the casing 28 will result in the sliding of base |64 in the guides |63 due to the action of the eccentric position of the stud |53 upon the sides of slot |61, which sliding movement of yoke carried by the base |64 will rotate arm |16, shaft |69 and arm |1| and result in a longitudinal movement of link |16 which will tilt cradle 45 to apply the cross trail correction to telescope 36. A pin |8| is passed through a hole in stem |49 to insure the proper positioning of the head |58.

The spindle 23 is rotatably mounted in a sleeve |82 (Fig. 20) secured in the azimuth stabilizer casing 35 by a Screw |83 and having a shoulder |84 upon which seats the shoulder |85 on spindie 29. An arm |86 (Fig. 23) is rotatable on the `of the gear 252 or 2|3.

enlarged upper vportion of spindle-29 where it is clamped in Aposition between a flange |81 and a bearing strip 4|88 that lies lagainst the bottom of casing member 28. At oneend of arm v|86 is an aperture |89 to receive a pin |99 by means of which the arm is connected to a link |9| that is also pivotally connected to clutch |92. At the other end of arm |86 is a gear sector 93 that meshes with la worm gear |94 (Fig. 23) on one end of a shaft |95 (Fig. 5) having a knob |99 on its other end. The jaws `of clutch |92, which are preferably of -a composition such as that known by the trade .nameof Micarta, are disposed to grip a drum |91 that is connected to the cardan of azimuth stabilizing gyro |93 (Fig. 22). The clutch mechanism (Figs. 18 and 19) vconsists of a member |99 connected at one end to jaw 209 of clutch |92 and slidable in jaw 201 thereof. A spring 200 held under variable compression by means of a washer 20|` and a nut 202 that is threaded on memberl |99, .bears against the jaw 201 in which member |99 is slidable and tends to move the jaws into clamping position upon drum |91. A lever 203 is lxed to a shaft 204 that is rotatable in the clutch jaw 201, the intermediate portion of the shaft being cut away to leave an eccentrically disposed portion 205 that bears against a member 298 so placed as to be capable of exerting a thrust against jaw 206. When lever 203 is .turned to cause eccentric portion .205 to bear against member 208, the jaws are separated and drum |91 may rotate independently of the clutch, but when the eccentric portion is turned away from member 208 the spring 200 draws the jaws together and engages the clutch with drum |91. A spring 209 on member 208 causes that member to remain in light contact with eccentric portion 205.

A servomotor 2|0 (Fig. 21) drives a -gear 2li which, in turn, through a train of reducing gears, i.

drives gears 2|2 and 2|3 in opposite directions. Upon the shafts of gears 2|2 and 2|3 are respectively the clutch plates 2|4 Vand 2|5 and gears 2|6 and 2 |1 xed to the clutch plates, the clutch plates and their associated gears being freely rotatable upon the respective shafts. Rockable armatures 2|8 and 2.|9 are so connected toclutch plates 2|4 and 2|5 vas, to move the clutch ,plates into frictional driving contact with the faces of gears 2|2 and 2|3 when .drawn toward 'the solenoids 220 and 22|. Upon the casing of gyro |98 is secured a'lightcommutator brush 222 (Figs. 22, 27) that rides over a commutator carried by cardan 223 of gyro |93. .As shown more plainly in Fig. 27, this commutator consists of a central vinsulating segment V224 with conducting segments 225 vand 226 on each side thereof and a second pair of .contact Ysegments 221 and .2.28 separated .respectively from .segments .225.v and 225 by .insulating means 229.

The spin axis .of gyro |98 is horizontal, the relative direction thereof with respect to the fore-A and-aft line of the craft being immaterial since this gyro is solely to impart directional stability to the sight casing. Any tilting of the spin axis of gyro |98 from the horizontal will result in the movement of brush 222 over the commutator segments associated therewith, resultingin a flow of current to one of the solenoids 220 or 22| whereupon the rockably mounted armature 2 I3 or 2 i9, as the case may be, will be attracted by the energized solenoid and will move the clutch disk connected thereto into driving contact with the facey The pinion 2|5 or 2|1 associated with the clutch disk so actuated will impart, through a suitable train of gears, to the ring gear230 on cardan 223, the driving force exerted by the servomotor 2|0 upon the gear 2|2 or 2|3, which will apply a precessing torque to the gyro in the proper -direction to bring the spin axis thereof back to the horizontal.

The purpose in using two conducting segments on each side of neutral insulating segment 224 is to obtain smoother action in the gyro precessing mechanism aboveidescribed. As shown in Fig. 27, the conducting segments'225 and 229 are connected through resistances 23| and 222 respectively to the slip rings 233 and 234 on the cardan 223 from which the current is taken by brushes 235and 2355 to the solenoids 220 and 22|. Consequently, if the spin axis 0f gyro |98 be but slightly displaced from the horizontal, the current transmitted to the solenoid involved will be reduced by the resistance inthe circuit. However, if the spin axis be displaced sufficiently -to move the brush into contact with one of the segments 22l or `228, the resistance shunted out and the full strength of the currentis applied to restore the gyro. As shown in Fig. 22, va lug 231 is provided on the casing of gyro V| 98 to contact the casing 39 and prevent tilting of the spin axis sufficiently to move brush 222 off the outer end of either of segments 221 or 228.

Drum |91 is connected by means of shaft 232 to the cardan 223 and when clutch |92 is engaged Iwith the drum, the sight casing will be stabilized in azimuth by gyro |99, but when it is desired to rotate the sight casing independently, clutch |92 is disengaged from drum |21 which permits free rotation of sightcasing spindle 29 in sleeve |82.

It is essential that the bomber be able to direct the `pilot uponthe course to be flown and for this purpose a pilot director system is .associated with the sight. A scale 239 (Fig. 3) is mounted on the upper side of casing 30 to cooperate with an index 240 carried by lower casing member 2S, the zero point of scale 239 being so disposed that when index 240 is in coincidence therewith the sight casing is at right angles to the foreand aft line of the craft. A pilot director brush 24! (Fig. 3,) is disposed to move in contact with a commutator 242, with Vits tip adjacent a scale 24? that indicates deviation of brush 2M from the fore-and-aft direction. Brush v2M is mounted on an arm 244 (Fig. 20) that is secured to a member 245 in frictonal engagement with a sleeve 245 carried by a gear 241 that `isconcentric with and rotatable upon sleeve -.|82, the frictional contact of member 245 with sleeve 246 being such that so longas brush 24| is freely movable. it will be shifted by rotation of gear 241 but when the brush contacts la limit stop (not shown) at either end of the commutator, the member 225 will slip on sleeve 245. A worm gear 248 (Fig. 5) is driven by means of gears enclosed in housings 249 and 250, the gear in the latter housing being fixed on a hollow shaft 25| that encloses shaft E95 and has a knob 252 on its outer end, shaft 25| being journaled in a bracket 259 carried by the sight casing in a manner to prevent longitudinal movement of the shaft. By means of knob 252 and parts connected thereto, gear 241 may be rotated to move brush 24| over commutator 242. Also. worm 248 and the vassociated members form the connection between gear 241 and the sight casing such that rotation of the sight casing about its vertical axis will move the brush 22| over come mutator y242 and therefore any deviation of the craft from a course set by the bomber will be inwill displace brush 24| dicated by displacement of brush 24| on scale 24S. When knob |98 is turned the pilot director brush 24| is rotated, Within the limits of its possible movement, at the same rate as the sight; when knobs 96 and 252 are turned simultaneously at the same rate the brush moves 5.2 times as fast as the sight for over-correction to bring the plane more quickly upon a collision course.

As shown in Fig. 27, the commutator 242 is connected to a pilot director indicator 254 that is in a position Where it is readily observable by the pilot. Since, when clutch H92 is engaged with drum 191 the bomb sight casing is stabilized by gyro |98, any change in the course of the craft Will result in a relative movement between the bomb sight casing and stabilizer casing 38 and over commutator 242 which displacement will be transmitted to pointer 255 of indicator 254 and will show to the pilot the direction and number of degrees of such deviation.

The wiring diagramof the bomb sight, the directional stabilizer and the pilot director are shown in Fig. 27. rEhe positive and the negative terminal of battery 256 are connected to binding posts 251 and respectively, of terminal block 259 mountedfon the side of stabilizer housing 39. The cord 259connects to the terminal block 259 through sight switch 26| to the terminal block 262 carried by the removable end portion 263 of the sight casing, in which portion are mounted servomotor t and the contact point 63 controlled by governor 82. To avoid the necessity of disconnecting wires from binding posts when the portion 2&3 is removed, spring contacts 294 are provided on the i'lXed portion of the casing and cooperate with like spring contacts 255 on portion 253 to complete the circuit. A switch 255 controls the supply of current to servomotor 6D. Wires 261 supply current to the lamp 298 which illuminates the upper surface of bomb sight gyro 34 and to gyro 34- through iiexible leads 299, wires 219 carried by cardan 83 and flexible leads 21| from the cardan to the gyro. A switch 212 connects servomotor 2|8 to terminal block 259 and switch 213 controls the current supply to directional gyro |98 and brush 222 through brushes 214 and slip rings 215 on cardan 223. The current supply to the pilot director system is controlled by switch 242 Operation Before a bombing run is started, switch 265 should be closed to start servomotor 69, and the correctness of the speed thereof determined by engaging a tachometer with tachometer connection 216 that is mounted on an extension of the servomotor shaft. This determination should be made for several of the altitudes shown on altitude knob 54 since it is essential to accurate functioning of the sight that disk 55 rotate at the correct speed for the altitude calibrations on the knob 54 for the type of bomb being used since, as above explained, a diiferent knob 64 is employed for each type of bomb.

As the objective is neared, servomotor 68, sight gyro motor 34, stabilizing gyro |98 and servomotor 219 are started, trail correction lever |42 is set for the speed of the plane and the altitude from which the bombs are to be dropped, the cross trail correction mechanism is adjusted, and altitude knob 54 also is set at the bombing a1- titude. Assuming the bombing altitude to be reached and the target to be in sight, the bomber releases clutch |92 from drum |91 and swings the sight casing back and forth which causes movement of pointer 255 back and forth over the scale of pilot indicator 254 and noties the piloi| that the bomber` is prepared to indicate the course to be followed. When the plane is on the desired course the bomber eifects a rough sight on the target by means of the open sight comprising parts 211 and 218 after which the target is picked up through telescope 36, the brush 24| is set at the zero point of scale 243 and clutch |92 is engaged with drum |91, which stabilizes the sight casing in azimuth, the telescope 36 being continuously vertically stabilized by gyro 34.

Knob |35 is pushed into mesh pinion |38 with pinion 88 and the knob is then rotated to bring the telescope approximately on the target, the fine sighting adjustment of the telescope being accomplished by pushing in head |92 to clutch knob H2, through gears |34 and 35, to gear 11. Knob |24 is rotated to set roller 61 at a distance from the center of disk such that the telescope will be driven through gears 18, 1|, 12, 13, differential gears 15, 11 and bar 8| at a speed that will keep the telescope on the target. The setting of knob |24 should be effected by observing whether` the horizontal cross line of the telescope remains on the target or drifts off; in the former case the setting is correct but in the latter case roller 51 must be moved on disk 65 until the cross line does remain on the target.

It is to be noted that pushing head |32 inwardly connects knob |23 to gear 11 of the differential mechanism and that the friction between the shaft upon which knob |23 is mounted and the bearing therefor` is sufficient to hold gear 11 against rotation and hence the movement of gear 13, which is intermediately driven from disk G5, will be transmitted to ground speed bar 8| and thence to radial slot lever 83 which is connected to ground speed segment 84. Through gear meshed with teeth 85 on segment 84 the movement is transmitted to cable drum 54 and thence by cable 58, cable drum 49 and pinion 48 to telescope 3S which is rotated on its trunnions in such direction that the upper end thereof approaches the vertical. The positiorn'ng of roller 54 on disk 55 by means of knob |24 results in the simultaneous setting, through gears 93 and 94, shaft 95, pinion 98 and range bar 91, of index iil on range segment |99 to indicate the range angle or dropping angle. As ground speed segment 84 continues to rotate, the notch 81 in the periphery' thereof is moved toward arm |93 of the automatic release switch and as index 88 on the ground speed segment approaches alignment with index lil, the bomber lifts up on lever I!) and so moves linger |89 to permit the arm |83 to drop into notch 81 which allows spring |08 to close the automatic release switch and drop the bomb; as soon as the bomb has been launched, lever I9 is released which immediately reopens the automatic release switch.

I claim:

1. A bomb sight, comprising a sighting device mounted to be rotatable in a substantially ver K, tical plane, means to stabilize said device with1 respect to the verticalfvariable speed means settable so to rotate said device as to retain in the field thereof a reference object moving relatively thereto; means settable to correct the speed of said variable speed means for the trail angle of a bomb including a lever calibrated in terms of altitudes and a plate over which said 'ens/4,397

' lever is movable, 'said plate yhaving inscribed on `it curves showing the characteristics lof fall of yaibornb at different speeds of a craft troni which the bomb is dropped, 'the altitude calibrations on-saidlever being-each registrable with a point on each of said curves; means settable to cor- Arect automatically the position of said .sighting device for the cross-trail of a bomb and means to stabilize all :the foregoing elements in azimuth. 2. AV bomb sight, comprising a sighting device mounted to be -rotatable in :a Vsubstantially vertical plane, means to stabilize said device with vrespect to the vertical,variable speed means setv`table so to rotate :said device as to retain in the field thereof a vreference object moving relatively thereto; means settable to correct .the speed of said lvariable speed means for the trail angle of 'a bomb including a lever calibrated in terms of :altitudes and a plate over Whichsaid lever is movable, :said plate having inscribed Aon lit curves showing 'thefcharacteristics of fall of a bomb at different speeds of a. craft from which the bomb =is dropped, the altitude `calibrations on said lever nbeing each registrabl'e with la point on .each oi said curves; yand means `settable to correct auto- A matically the position of said sighting device for the vcross-trail of a bom-b.

3. A Vbomb sight, comprising a sighting device .vmountedto be rotatable in a substantially vertical plane, ymeans to stabilize said-device with re- .zspect tothe vertical, variable speed means set- 4table so to .rotate said device as to retain in the eld thereof .a reference `obj ect .moving relatively ithereto; .and means settable to correct the speed vof said variable speed means for the trail angle xoi a kbomb including `a llever calibrated in terms 'ofialtitudes and. a plate over Whichsaid .lever is movable, .said plate `having inscribed on it curves showing the characteristics of fall of a bomb at different speeds of a craft from which the bomb dropped, thealtitude calibrations on said lever .being each registrable With a point on each of said curves.

4, A l.bomb sight, comprising a sighting device mounted to be rotatable in a substantially vertical plane, means to stabilize said device with re- `an axis transverse to the longitudinal axis of said "device, driving connections between said roller andsaid sighting device; means lto adjust the rate at which ysaid roller is ldriven to correct for the trail angle of a bomb including a lever calibrated in terms of'altitudes', a plate over which said lever is movable, said plate having inscribed on it `curves showing the ycharacteristics of fall of la bomb lat different speeds of a craft from which the bomb is dropped, the altitude calibrations on said -leverbeing each registrable with a point on each -of saidcurves, means connecting said roller tofsaid` lever whereby movement of the lever shifts said roller on said disk; means including a vertically disposed spindle to support all the foregoing elements; and means vto change automatically the position of said sighting device to correct for `the cross-trailfof a bomb including a yoke mounted to Slide transversely of the plane of rotation of the sighting device and having a .slottedV base, Athe slot in said base being disposed above 'the longitudinal .axis of said spindle, a stud disposed in said slot land mounted to be slidable ytransversely of the Said spindle axis, means so to slide said stud proportionally to the cross-trail of .a bomb, a rockable shaft, an arm connected at one end to said shaft and having at the other end a ball disposed in said yoke, a second arm connected to said shaft and means connecting said second arm to the sighting device.

5. A bomb sight, comprising a sighting device 'mounted to be rotatable about an axis transverse to the `longitudinal axis of the device, means to rotate said device about said transverse axis at a rate that is afunction of the altitude .and ground speed of a craft upon which the sight is carried, a vertical spindle by which the foregoing elements are supported; and means to shift the orientation cf said transverse axis to correct for the cross trail of a bomb including a yoke mounted -to slide transversely of the plane -of rotation oi the vsighting device and having a slotted base, the Aslot in said base being disposed above the longitudinal axis of said spindle, a stud disposed in said slot and. Vmounted Vto be slidable transversely `of said spindle axis, means including an element calibrated in degrees to slide said stud proportionally to the cross-trail of a bomb, a rockably mounted shaft, an arm connected at one end to said shaft and having at the other end a ball `disposed in said yoke, a second ,arm connected to said shaft and means connecting saidsecond arm to said sighting device.

6. A vbomb sig-ht, comprising a casing, an axially ybored spindle upon which said casing is mounted, a cardan journalled in said casing, a cradle journalied in said cardan and lying transversely thereof, a sighting device mounted in said cradle to rotate in a plane that includes the journals of the cradle, a gyro mounted in said cardan and connected to said device to stabilize said device vertically, a stem disposed in the bore of said spindle, said stem having at one end an elongated head lying With its greatest dimension transversely of the casing, an upstanding stud operatively connected to said head to slide longitudinally thereof, a strap operatively Yconnected to said stud, means including an element calibrated in degrees of cross-trail of a bomb to move said .strap and adjust the position of said stud proportionally to such cross-trail, a yoke mounted to Vbe slidable longitudinally of said casing and having in its base a slot in which said stud is siidable, arockably mounted shaft, an arm connected at yone rend to said shaft and having at its other end a ball that is disposed in said yoke, a second arm connected to said shaft and means connecting said second arm to said cradle.

7. A bomb sight, comprising a casing, an axially bored spindle upon which said casing is mounted, a cardan journalled in said casing, a cradle jo-urnalled in said cardan and lying transversely thereof, a sighting device mounted in said cradle to rotate in `plane that includes the journals of the cradle, a gyro mounted in said `cardan and connected io device to stabilize said device vertically, means associated with and settable eccentrically or said spindle proportionvally tothe cross-trail of a bomb, a. yoke connected vto said member to be slid thereby longitudinally of said case when said member is eccentrically positioned and the casing is rotated about the axis of the spindle, and a vsystem including lever .arms and links connecting said yolse to the cradle torock said cradle and change the plane of rotation of .said .sighting device when said casing is l rotated about the axis of the spindle While the said member is eccentrically positioned.

8. A bomb sight, comprising a casing, an axially bored spindle upon which said casing is mounted, a cardan journalled in said casing, a cradle journalled in said cardan and lying transversely thereof, a sighting device mounted in said cradle to rotate in a plane that includes the journals of the cradle, a gyro mounted in said cardan and connected to said device to stabilize said device vertically, means associated with and settable eccentrically of said spindle proportionally to the cross-trail of a bomb, and means connecting said member to said sighting device to shift the plane of rotation of said device proportionally to the eccentricity of said member when said casing is rotated about the axis of the spindle while said member is eccentrically positioned.

9. A bomb sight, comprising a sighting device rotatable about an axis transverse to the longitudinal axis thereof, mechanism so to rotate Said device at a rate that is a function of the altitude of the axis of such rotation and of the speed thereof with respect to the ground, means to change the said rate to correct for the trail of a bomb whereof the angle of dropping is controlled by said device and means to shift the plane of rotation of said device with respect to the other elements of the sight to correct for the cross-trail of such bomb.

10. A bomb sight, comprising a rotatably mounted sighting device; mechanism to rotate said device including a rotatable disk, means to adjust the speed of rotation of said disk inversely proportionally to altitude, a roller driven by said disk, means to set the position of said roller on said disk proportionally to ground speed, a member whereof the position is determined by the last mentioned means, ground speed indicating means including a drum connected to and actuated by said member and an index to define the point on said drum at which the ground speed is to be read.

l1. A bomb sight, comprising a rotatably mounted sighting device; mechanism to rotate said device including a rotatable disk, means to adjust the speed of rotation of said disk inversely proportionally to altitude, a roller driven by said disk, means to set the position of said roller on said disk proportionally to ground speed, a member whereof the position is determined by the last mentioned means, said member having on it a toothed rack, a pinion meshed with said rack, a ground speed indicating drum connected to said pinion and an index to define the point on said drum at which the ground speed is to be read.

12. A bomb sight, comprising a rotatably mounted sighting device; mechanism to rotate said device including a rotatable disk, means to adjust the speed of rotation of said disk inversely proportionally to altitude, a roller driven by said disk, means to set the position of said roller on said disk proportionally to ground speed, a member whereof the position is determined by the last mentioned means, a rotatable ground speed indicating drum, a iiexible cable partly wound upon and having one end attached to a portion of said drum and its other end attached to said member, resilient means tending to rotate said drum in such sense as to wind said cable thereon and an index to define the point on said drum at which the ground speed is to be read.

CTI.

13. The combination with a bomb sight having a sighting device and supporting means therefor including a spindle, of a sleeve in which said spindle is rotatably mounted, a gear having an elongated hub rotatably mounted upon said sleeve, a friction sleeve disposed on said elongated hub, an arm secured to said friction sleeve, an electrically conducting brush carried by said arm, a commutator with which said brush is in contact and over which it is movable, stops to limit the angular movement of said brush, the frictional engagement of the said friction sleeve with said elongated hub being such that said sleeve slips on said hub when the brush contacts a stop, means connecting said gear to the said supporting means to move said gear either in unison with said supporting means or relatively thereto, a scale adjacent the free end of said brush to indicate the angular position of said brush between said stops and a remote indicating instrument connected to said brush and said commutator to reproduce the positional indication of said brush.

14. The combination with a bomb sight, of means connected thereto to stabilize said sight in azimuth, comprising a gyro with its spin axis normally horizontal, a cardan in which said gyro is pivotally mounted, a commutator mounted on said cardan having a neutral insulating segment and on each side thereof two conducting segments, the segments on each side of the neutral segment being separated by insulating material, means energizable by current through said commutator to precess said gyro, the sense of such precession depending upon which side of said neutral segment the conducting segment in the circuit is on, a resistance connected between each conducting segment next the neutral segment and said precessing means, and a brush carried by the case of said gyro in position to contact said neutral segment when the axis of the gyro is horizontal but movable to contact with a conducting segment when said gyro aXis is deected from the horizontal.

15. The combination with a bomb sight having a vertically extending supporting spindle, of means to stabilize said sight in azimuth comprising a gyro having its spin axis normally horizontal, a cardan in which said gyro is mounted, the axis of rotation of said cardan being vertical, a drum connected to said cardan to be rotated therewith, a clutch disposed around said drum having a face substantially conforming to the contour of said drum, means tending to hold said clutch in frictional engagement with said drum, means to move said clutch out of engagement with said drum against the action of said next preceding means and means operatively to conneet said clutch to said spindle.

16. A bomb sight for aircraft, comprising a sighting device, a first means to stabilize said device in a vertical plane, a second means to maintain said vertical plane in a set position in azimuth regardless of changes of course of the aircraft upon which said sight is mounted, and means to engage said second means operatively with, or disengage it from, said sighting device.

17. A bomb sight for aircraft, comprising a sighting device, a rst means to stabilize said device in a vertical plane, a second meansto maintain said vertical plane in a set position in azimuth regardless of changes of course of the aircraft upon which said sight is mounted, means to eng-age said second means operatively with, or disengage it from, said sighting device, and means 

